Pamela Smart on Affair with Student That Led to Murder: 'I Knew Better'

In an exclusive interview with PEOPLE, the former New Hampshire school administrator – who was convicted in 1991 for persuading her then 16-year-old student lover, William "Billy" Flynn, to kill her husband Gregg – expresses regret and remorse about that affair. But she insists, as she has from the start, that she is innocent, despite her sentence of life without parole.

"If I wouldn't have made this horrible choice to get involved with him, would my husband still be alive? Probably," says Smart, in a sit-down interview at the Bedford Hills Correctional Facility for Women in New York.

"I was in a situation where I knew better. And I shouldn't have made the decision that I did to be involved with him," she says. "It took me many years to see my own responsibility."

Now, aided by a new HBO documentary, CAPTIVATED The Trials of Pamela Smart, which re-examines the feverish media attention around the case that inspired the 1995 film To Die For, and the disparity in the lesser sentences handed down to Flynn and his three convicted teen conspirators in the murder, Smart hopes for a reconsideration of her own sentence. The confessed triggerman, Flynn, is up for parole next year.

Smart also tells PEOPLE about building a life for herself behind prison walls, and working to make a difference for others where she can.

"Each day that's in front of us is an opportunity to do something with our lives, wherever we are," she says.

See below for an exclusive first look at HBO's documentary, which airs Aug. 18.

For more on Smart's life now, pick up this week's issue of PEOPLE, on newsstands Friday